TECHNOLOGICAL QUALITY AND UTILIZATION
OF POTATO TUBERS
José Carlos Feltran1; Leandro Borges Lemos2*; Rogério Lopes Vieites3
1
UNESP/FCA - Programa de Pós-Graduação em Agronomia.
2
UNESP/FCA - Depto. de Produção Vegetal, C.P. 237 - 18603-970 - Botucatu, SP - Brasil.
3
UNESP/FCA - Depto. de Gestão e Tecnologia Agroindustrial, C.P. 237 - 18603-970 - Botucatu, SP - Brasil. *Corresponding author <leandrobl@fca.unesp.br >
ABSTRACT: Increasing concerns have been verified with regard to the quality factor of potato tubers and their correct form of use and consumption. The purpose of this research was to determine the technological quality of potato tuber cultivars and identify the best forms of use and consumption. A completely randomized experimental design was adopted with 18 treatments represented by cultivars Agata, Apuã (IAC-5977), Aracy (IAC-2), IAC Aracy Ruiva, Asterix, Bintje, Dali, Clone IAC-6090, Itararé (IAC-5986), Laguna, Remarka, Liseta, Mondial, Novita, Oscar, Picasso, Santana, and Solide, with four replications. Specific gravity showed a positive correlation with starch content, texture, pulp pH, and soluble solids, and was negatively correlated with reducing sugars. The technological characteristics represented by specific gravity, dry matter content, texture, starch content, reducing sugars, pulp pH, titrable acidity, and soluble solids are influenced by genotype or cultivar. Cultivars Oscar, Itararé, IAC Aracy Ruiva, Clone IAC-6090, Aracy, Solide, Asterix, Santana, and Laguna were outstanding with best characteristics for frying, mashing and roasting. Mondial, Picasso, Novita, Dali, and Agata are appropriate for boiling, and more specifically for salads. In turn, potato cultivars Apuã, Remarka, Bintje, and Liseta are suitable for mashing and for roasting.
Key words: Solanum tuberosum, dry matter, reducing sugars, starch content
QUALIDADE TECNOLÓGICA E UTILIZAÇÃO
DE TUBÉRCULOS DE BATATA
RESUMO: Atualmente tem ocorrido crescente preocupação com o fator qualidade da batata e a forma correta de utilização para o consumo. O objetivo deste trabalho foi determinar a qualidade tecnológica dos tubérculos de cultivares de batata, visando identificar a melhor forma de utilização e consumo. O delineamento experimental foi inteiramente casualizado com 18 tratamentos, representados pelos cultivares Agata, Apuã (IAC-5977), Aracy (IAC-2), IAC Aracy Ruiva, Asterix, Bintje, Dali, Clone IAC-6090, Itararé (IAC-5986), Laguna, Remarka, Liseta, Mondial, Novita, Oscar, Picasso, Santana e Solide, com quatro repetições. O peso específico apresentou correlação positiva com o teor de amido, textura, pH de polpa e sólidos solúveis e negativa com os teores de açúcares redutores. As características tecnológicas representadas pelo peso específico, teor de matéria seca, textura, teor de amido, açúcares redutores, pH da polpa, acidez titulável e teor de sólidos solúveis são influenciadas pelo genótipo ou cultivar. Destacaram-se, com melhores características para fritura, purê e assada os cultivares Oscar, Itararé, IAC Aracy Ruiva, Clone IAC-6090, Aracy, Solide, Asterix, Santana e Laguna. São apropriados para o cozimento e especificamente para salada os cultivares Mondial, Picasso, Novita, Dali e Agata. Já os cultivares Apuã, Remarka, Bintje e Liseta são adequados para purê e assadas. Palavras-chave: Solanum tuberosum, matéria seca, açúcares redutores, teor de amido
INTRODUCTION
At present, the characteristics required by the po-tato-consuming market in Brazil are experiencing trans-formations with respect to fresh and industrial quality. Potato chips are predominant and are the consumer’s pre-ferred type in potato industrialization. In the fresh mar-ket, consumers select potatoes by visual characteristics such as shape, color, and skin brightness. However, there has been an increasingly higher search for information on the part of consumers with regard to appropriate uses of the product, that is, for frying, baking, salads, or
mash-ing. Between 90 and 98% of the domestic potato yield have been sold fresh, and almost all of it is used by con-sumers in the form of potato fries (Lopes & Buso, 1997); an expressive amount is also consumed in baked form.
exists with dry matter content (Schippers, 1976), and a negative correlation exists with reducing sugars content (Iritani & Weller, 1974; Salamoni et al., 2000).
Also, a nonenzymatic browning develops during the frying process, which has been attributed to a reac-tion between reducing sugars (glucose and fructose), the amino acid lysine, and proteins (known as Maillard re-action); as the frying process is extended, the product may become burned (caramelization), resulting in a bitter off-flavor. A low content of reducing sugars limits the ex-cessive browning of the final product (Gould, 1988). Kadam et al. (1991a) verified a variation from 0.5 to 2.0% in reducing sugars contents in potato tubers. In turn, tu-bers with contents higher than 2% are unacceptable for frying (Pereira, 1987).
Other factors that may interfere in a negative and/ or indirect way on the technological quality of tubers are pulp pH, total acidity, and starch content. The pH index determines deterioration potential by fermentation and the activity of enzymes (Cecchi, 1999). The phosphorylase enzyme acts predominantly on starch breakdown (Jadhav et al., 1991), with maximum activity at pH 5.5 (Iritani & Weller, 1973). Invertase, on the other hand, promotes su-crose breakdown into glucose and fructose (Sowokinos, 1990), and presents an optimum point at pH 4.7 (Pressey, 1966). In addition, pulp pH is variable and presents a negative correlation (-0.86) with reducing sugars accu-mulation (Iritani & Weller, 1973). In turn, the total acid-ity parameter quantifies organic acids present in foods and, in general, there is a tendency of reduction in their contents because of respiration and/or due to conversion into sugars (Chitarra & Chitarra, 1990), which could con-tribute toward browning of the fried product.
Starch comprises 65-80% of the dry weight of tu-bers; however, variation in starch is mainly due to genet-ics (Pereira, 1987; Kadam et al., 1991a). Since starch comprises the largest part of dry matter, it has direct in-fluence on technological quality, especially with regard to the texture of the processed products (Kadam et al., 1991b).
The objective of this work was to determine the technological quality of potato cultivar tubers, in order to identify their best forms of use and consumption.
MATERIAL AND METHODS
Large-sized potato tubers of several cultivars, from plantings carried out during the 2000 “das águas” season in the municipality of São Manuel, SP (22º44’ S; 48º34’ W), were used in the experiment conducted un-der laboratory conditions. The experimental design was completely randomized, with four replicates and 18 treat-ments, represented by potato cultivars Agata, Apuã (IAC-5977), Aracy (IAC-2), IAC Aracy Ruiva, Asterix, Bintje, Dali, Clone IAC-6090, Itararé (IAC-5986), Laguna,
Remarka, Liseta, Mondial, Novita, Oscar, Picasso, Santana, and Solide.
Tuber technological characteristics such as spe-cific gravity, dry matter content, texture, starch content, reducing sugars, pulp pH, titrable acidity, and soluble sol-ids content were evaluated. In order to accomplish these determinations, recently-harvested tuber samples were collected and then washed, shade-dried, and taken to the laboratory for analytical procedures.
The tubers were weighed in open air and in wa-ter, on a hydrostatic precision balance, for specific grav-ity determination. Tuber dry matter content was calculated indirectly using the specific gravity results, following a methodology by Schippers (1976). Four readings were taken from each tuber for texture determination, by means of a texturometer with a 20-mm penetration distance and a 2.0 mm s-1 speed, using a TA 9/1000 probe tip. The starch content was quantified in tubers dried in a forced air circulation oven at a temperature near 70ºC until con-stant weight was achieved, and later ground in a Wiley type, stainless steel mill; determinations were made ac-cording to the methodology proposed by AOAC (1992).
Reducing sugars content was quantified in 50 g pulp samples according to methodology by Nelson (1944) and Somogy (1945); readings were made in a digital spec-trophotometer at 535 nm. The pH readings were deter-mined in 50 g samples of pulp ground with 100 mL dis-tilled water, in a digital pH-meter. For titrable acidity de-termination, 50 g of pulp ground with 100 mL distilled water were used; the mixture was filtered and titrated with a 0.10 mol L-1 sodium hydroxide solution, using phenol-phthalein as end point indicator, in a digital pH-meter with a potentiometer capable of measuring pH values of up to 8.1. For soluble solids quantification, the juice ex-tracted from a slice of the tubers was used. Two droplets of juice were used; the droplets were placed on the prism of an electronic refractometer; the oBrix reading was taken after one minute.
Data were submitted to analysis of variance us-ing the F test and means were compared by Tukey test at 5%. Several tuber characteristics were correlated, in or-der to determine the degree of association between them and the data were compared at P < 0.01; P < 0.05, and P < 0.10.
RESULT AND DISCUSSION
results for frying belong to the interval from 1.0701 to 1.0850 kg L-1, that is, Solide, Aracy, Itararé, IAC Aracy Ruiva, Oscar, and Clone IAC-6090, while ‘Mondial’ showed the poorest performance for this cooking proce-dure.
With respect to dry matter content, a classifica-tion identical to that of specific gravity was observed. ‘Clone IAC-6090’ and the Mondial cultivar presented extreme values, at 22.4 and 15.7%, respectively. The val-ues for dry matter are below the minimum intervals re-quired for obtaining fried products with excellent char-acteristics, as described by Gravoueille (1997). The ex-ceptions were cultivar Oscar and the Clone IAC-6090, which showed dry matter values of 21.5 and 22.4%, re-spectively. Cacace et al. (1994) suggested that dry mat-ter content values should be assembled into three groups: high dry matter content (contents higher than 20.0%), intermediate dry matter content (contents be-tween 18.0 and 19.9%), and low dry matter content (contents lower than 17.9%). Therefore, according to this classification, cultivars Aracy, Itararé, IAC Aracy Ruiva, Oscar, and Clone IAC-6090 belong to the high
dry matter content group. Conversely, ‘Remarka’, ‘Apuã’, ‘Laguna’, ‘Santana’, ‘Asterix’, and ‘Solide’ were categorized in the group showing an intermediate dry matter content. The low dry matter content group, in turn, comprised ‘Mondial’, ‘Novita’, ‘Dali’, ‘Agata’, ‘Picasso’, ‘Liseta’, and ‘Bintje’. According to Brune et al. (1994), cultivar Bintje showed a dry matter content of 19%, and was therefore classified as having medium dry matter content, in disagreement with this work’s re-sults. This is due to the genotype × environment inter-action effect, since variations in dry matter contents of tubers from the same cultivar produced in different en-vironments are common (Beukema & Zaag, 1990; Cacace et al., 1994; Melo, 1999).
The specific gravity variable showed a positive correlation with starch content (r = 0.51; P < 0.05), and a negative correlation with reducing sugars contents (r = -0.58; P < 0.05) (Table 3), confirming results by Salamoni et al. (2000) and Gould (1988). It is also interesting to point out that specific gravity showed a positive correla-tion with texture (r = 0.82; P < 0.01), pH (r = 0.55; P < 0.05), and soluble solids (r = 0.44; P < 0.10).
Cultivar Specific gravity Dry matter Texture Starch
kg L-1 % N %
AGATA 1.0560 ghi 16.4 ghi 6.74 fg 66.0 abcd
APUÃ (IAC-5977) 1.0650 defg 18.4 defg 8.15 abcde 68.2 abc
ARACY (IAC-2) 1.0737 abcd 20.3 abcd 8.04 abcde 71.4 a
IAC ARACY RUIVA 1.0748 abc 20.6 abc 8.36 abc 69.6 ab
ASTERIX 1.0685 cde 19.1 cde 8.15 abcde 66.2 abcd
BINTJE 1.0628 efgh 17.9 efgh 7.39 bcdef 64.1 bcde
DALI 1.0546 hi 16.1 hi 7.32 cdef 61.0 de
CLONE IAC-6090 1.0831 a 22.4 a 8.50 ab 68.4 abc
ITARARÉ (IAC-5986) 1.0747 abc 20.5 abc 8.16 abcde 69.6 ab
LAGUNA 1.0661 cdef 18.6 cdef 7.64 abcdef 64.7 abcd
REMARKA 1.0632 efgh 18.0 efgh 8.55 ab 66.5 abcd
LISETA 1.0611 efghi 17.5 efghi 7.13 def 68.6 abc
MONDIAL 1.0527 I 15.7 i 7.01 efg 65.2 abcd
NOVITA 1.0543 hi 16.0 hi 5.97 g 65.9 abcd
OSCAR 1.0793 ab 21.5 ab 8.69 a 65.1 abcd
PICASSO 1.0584 fghi 16.9 fghi 6.83 fg 57.6 e
SANTANA 1.0666 cdef 18.7 cdef 8.19 abcd 62.5 ed
SOLIDE 1.0706 bcde 19.6 bcde 8.28 abcd 66.5 abcd
Overall mean 1.0659 18.6 7.73 65.9
F test for:
Cultivars 23.096* 23.095* 11.668* 5.986*
CV% 0.35 4.43 5.74 4.13
lsd (Tukey at 5%) 0.0097 2.13 1.15 7.07
Table 1 - Specific gravity, dry matter content, pulp texture, and starch content of potato cultivar tubers.
The mean texture value for fresh tubers was 7.73 N, ranging between 5.97 and 8.69 N. Even though this variable presented a positive and significant correlation with specific gravity (Table 3), the results shown in Table 1 indicated that no direct relation exists, since cultivar Oscar showed the highest texture value (8.69 N), while ‘Novita’ showed the lowest (5.97 N), not corresponding to the cultivars with the highest and lowest specific
gravi-ties. Therefore, other unknown factors are present in tex-ture quantification.
Starch contents oscillated between 57.6 and 71.4%, in part confirming results obtained by Pereira (1987), since cultivars Picasso, Dali, Santana, Bintje, and Laguna showed starch values lower than those presented by that author. Cultivar Aracy, however, showed the highest starch content, while ‘Picasso’ showed the lowest content. Characteristics Texture Starch Reducing sugars Pulp pH Titrable acidity Soluble solids
Specific gravity 0.82*** 0.51** -0.58** 0.55** 0.00 0.44*
Texture 0.38 -0.44* 0.56** -0.13 0.44*
Starch -0.17 0.44* 0.48** 0.32
Reducing sugars -0.50** -0.10 0.12
Pulp pH -0.01 0.10
Titrable acidity 0.15
*Significant at P < 0.10, **Significant at P < 0.05, ***Significant at P < 0.01.
Table 3 - Simple correlation coefficients (r) between specific gravity, texture, starch and reducing sugars contents, pulp pH, titrable acidity, and soluble solids of potato cultivar tubers.
Table 2 - Reducing sugars contents and total titrable acidity, soluble solids, and pulp pH of potato cultivar tubers.
Means followed by the same letter in the column do not differ by Tukey test at 5%. *Significant at 5%.
Cultivar Reducing sugars Titrable acidity Soluble solids Pulp pH
--- % --- ° Brix
AGATA 0.82 abc 0.150 ab 5.46 bcd 5.56 ab
APUÃ (IAC-5977) 0.43 cde 0.155 ab 5.77 abcd 5.62 ab
ARACY (IAC-2) 0.55 abcde 0.170 ab 5.95 abcd 5.57 ab
IAC ARACY RUIVA 0.40 cde 0.178 a 6.23 abc 5.72 ab
ASTERIX 0.82 abc 0.145 ab 5.94 abcd 5.53 ab
BINTJE 0.51 bcde 0.160 ab 5.19 cd 5.57 ab
DALI 0.58 abcde 0.173 ab 5.70 abcd 5.57 ab
CLONE IAC-6090 0.61 abcde 0.158 ab 6.69 a 5.69 ab
ITARARÉ (IAC-5986) 0.32 de 0.165 ab 6.42 ab 5.68 ab
LAGUNA 0.49 bcde 0.145 ab 5.12 cd 5.94 a
REMARKA 0.87 ab 0.143 ab 6.72 a 5.61 ab
LISETA 0.58 abcde 0.173 ab 5.07 cde 5.45 ab
MONDIAL 0.96 a 0.165 ab 4.88 de 5.40 ab
NOVITA 0.72 abcd 0.158 ab 5.41 bcd 5.50 ab
OSCAR 0.35 de 0.148 ab 5.92 abcd 5.71 ab
PICASSO 0.61 abcde 0.140 b 5.32 bcd 5.16 b
SANTANA 0.52 bcde 0.140 b 5.55 abcd 5.59 ab
SOLIDE 0.26 e 0.145 ab 3.91 e 5.77 ab
Overall mean 0.58 0.156 5.62 5.59
F test for:
Cultivars 5.409* 3.243* 9.308* 1.950*
CV% 29.25 8.72 8.03 4.20
Oscillations in pH (5.4 to 6.2), titrable acidity (26.5 to 60.9 mL 100 g-1 NaOH), soluble solids (5.1 to 6.8 °Brix), and reducing sugars values (0.7 to 1.3%) were observed in six potato cultivars. Of these, cultivar Bintje showed values of 5.8 ± 0.4, 36.3 ± 6.9, 6.3 ± 0.5, and 1.1 ± 0.2, while ‘Aracy’ showed values of 5.7 ± 0.2, 44.3 ± 16.6, 6.1 ± 0.2, and 1.0 ± 0.3 for pH, titrable acidity, soluble solids, and reducing sugars, respectively (Paschoalino et al., 1983). Thus, cultivars Bintje and Aracy showed pH values similar to those obtained by the authors of this work. However, ‘Bintje’ showed lower soluble solids and reducing sugars values, while ‘Aracy’ obtained a similar soluble solids content and a lower re-ducing sugars content.
Cultivar Solide showed the smallest °Brix value (3.91), while ‘Remarka’ and ‘Clone IAC-6090’ showed the highest values, with 6.72 and 6.69 °Brix, respectively. Therefore, these two cultivars contain the highest sucrose values; however, according to Pereira (1987), these re-sults do not interfere with tuber quality. The texture vari-able showed a positive and significant correlation (P < 0.10) with soluble solids contents, in the order of 0.44 (Table 3). Cultivars Liseta, Mondial, and Solide showed lower values than those described by Paschoalino et al. (1983), while the other cultivars showed values within the described interval.
The correlation study between pH and reducing sugars contents (Table 3) showed a negative value (r = -0.50) and significance at P < 0.05, confirming re-sults obtained by Iritani & Weller (1973). The correla-tion showed a positive (r = 0.55) and significant value at P < 0.05 between variables specific gravity and pH. These results allow us to suppose that a high pH value favors specific gravity and a smaller reducing sugars content.
Cultivar Picasso showed the lowest pulp pH value (5.16), while ‘Laguna’ showed the highest value, at 5.94. The pH value for cultivar Picasso was lower than the in-terval reported by Paschoalino et al. (1983); the other cul-tivars showed pH values compatible with that interval. Tubers of cultivar Laguna have a greater probability of undergoing a faster fermentation than ‘Picasso’ tubers, since the sucrose breakdown process and the formation of reducing sugars are more favored in ‘Picasso’, in ad-dition to the fact that cultivar Laguna tubers showed greater propensity to undergo breakdown of starch mol-ecules.
The contents of reducing and/or non-reducing sugars are closely related to the quality of the final prod-uct; therefore, sugar content increases may negatively re-flect on this trait. There was little variation in titrable acidity percentage, ranging between 0.140 and 0.178%. Cultivars Picasso and Santana showed the smallest value (0.140%), differing from ‘IAC Aracy Ruiva’ (0.178%). Hence, cultivars Picasso and Santana showed a more suit-able behavior for this varisuit-able.
Cultivars ‘Oscar’, ‘Itararé’, and ‘IAC Aracy Ruiva’ showed suitable characteristics to be used as fried potatoes. The other cultivars showed dry matter contents lower than 20% and/or reducing sugars contents above 0.4%. However, based on the total solids contents found by Paschoalino et al. (1975) and Carvalho et al. (1977), ‘Clone IAC-6090’ and cultivars Aracy, Solide, Asterix, Santana, and Laguna can also be used for fries.
Baked tubers can be classified as either mealy or waxy (Kadam et al., 1991b). The mealy constitution is due to a high dry matter content; the tissues have a dry appearance and become immediately crumbled upon bak-ing, and physical disintegration of the tuber structure oc-curs. Mealy-textured tubers are preferred for roasted, mashed, and fried potatoes. Waxy-textured tubers display a moist appearance and less disintegration after cooking, and the tuber’s structure is left intact. These are suitable for making salads and creams. Therefore, cultivars Mondial, Picasso, Novita, Dali, and Agata are more ap-propriate for the preparation of salads, while ‘Apuã’, ‘Remarka’, ‘Bintje’, and ‘Liseta’ should be preferred for mashed and roasted potatoes. However, tubers used in boiling processes do not present guaranteed quality and consistency, because these characteristics are associated with intrinsic characteristics of the tuber, such as cell size, cell wall makeup, starch content, size, location, and char-acteristics of starch grains, and other physical variables such as time to become cooked and water temperature.
CONCLUSIONS
Technological characteristics represented by spe-cific gravity, dry matter content, texture, starch content, reducing sugars, pulp pH, titrable acidity, and soluble sol-ids content are influenced by genotype or cultivar.
Cultivars Oscar, Itararé, IAC Aracy Ruiva, Clone IAC-6090, Aracy, Solide, Asterix, Santana, and Laguna are suitable for frying, mashing, and roasting.
Cultivars ‘Mondial’, ‘Picasso’, ‘Novita’, ‘Dali’, and ‘Agata’ are suitable for boiling, and specifically ap-propriate to be consumed in the form of salads.
Tubers of cultivars Apuã, Remarka, Bintje, and Liseta are suitable for mashed and for roasted potatoes.
ACKNOWLEDGEMENT
To CNPq for financial support.
REFERENCES
ASSOCIATION OF OFFICIAL ANALYTICAL CHEMISTS. Official
methods of analisys of the AOAC. 11.ed. Washington, 1992. 1015p.
BEUKEMA, H.P.; ZAAG, D.E. van der Introduction to potato production. Wageningen: PUDOC, 1990. 208p.
Received October 02, 2003 Accepted September 13, 2004 CACACE, J.E.; HUARTE, M.A.; MONTI, M.C. Evaluation of potato
cooking quality in Argentina. American Potato Journal, v.71, p.145-153, 1994.
CARVALHO, R.; TRAVAGLINI, D.A.; MATSURA, P.T.; CABRAL, A.C.D.; MORI, E.E.M. Comportamento das variedades de batatinha Bintje e Radosa na obtenção de flocos de batatinha e fritas do tipo “chips”. Boletim do Instituto de Tecnologia de Alimentos, n.54, p.135-152, 1977.
CECCHI, H.M. Fundamentos teóricos e práticos em análise de alimentos. Campinas: UNICAMP, 1999. 212p.
CHITARRA, M.I.F.; CHITARRA, A.B. Pós-colheita de frutos e hortaliças: fisiologia e manuseio. Lavras: FAEPE, 1990. 320p.
GOULD, W.A. Quality of potatoes for chip manufacture. In: SYMPHOSIUM POTATO QUALITY INDUSTRY NEEDS FOR GROWTH. Fort Collins, 1988. Proceedings. Fort Collins: The Potato Association of the America. 1988. p.10-20.
GRAVOUEILLE, J.M. Maîtriser la teneur en sucres des tubercules. Pomme
de Terre Frites, n.502, p.39-46, 1997.
IRITANI, W.M.; WELLER, L. The development of translucent end tubers.
American Potato Journal, v.50, p.223-233, 1973.
IRITANI, W.M.; WELLER, L.D. Some factors influencing the pH of apical and basal portions of Russet Burbank and Norgold potatoes. American
Potato Journal, v.51, p.119-125, 1974.
JADHAV, S.J.; MAZZA, G.; DESAI, U.T. Postharvest handling and storage. In: SALUNKHE, D.K.; KADAM, S.S.; JADHAV, S.J. (Ed.) Potato
production, processing and products. Boca Raton: CRC Press, 1991.
cap.4, p.69-109.
KADAM, S.S.; DHUMAL, S.S.; JAMBHALE, N.D. Structure, nutritional composition, and quality. In: SALUNKHE, D.K.; KADAM, S.S.; JADHAV, S.J. (Ed.) Potato production, processing and products. Boca Raton: CRC Press, 1991a. cap.2, p.9-35.
KADAM, S.S.; WANKIER, B.N.; ADSULE, N.R. Processing. In: SALUNKHE, D.K.; KADAM, S.S.; JADHAV, S.J. (Ed.) Potato
production, processing and products. Boca Raton: CRC Press, 1991b.
cap.5, p.111-154.
LOPES, C.A.; BUSO, J.A. Escolha da cultivar. In: LOPES, C.A.; BUSO, J.A. (Ed.) Cultivo da batata (Solanum tuberosum L.). Brasília:
EMBRAPA, CNPH, 1997. p.3-4. (Instruções Técnicas, 8).
LULAI, E.C.; ORR, P.H. Influence of potato specific gravity on yield and oil content of chips. American Potato Journal, v.56, p.379-390, 1979. MELO, P.E. de Cultivares de batata potencialmente úteis para processamento na forma de fritura no Brasil e manejo para obtenção de tubérculos adequados. Informe Agropecuário, v.20, p.112-119, 1999.
NELSON, N.A. Photometric adaptation of Somogy method for the determination of glucose. Journal of Biological Chemistry, v.153, p.375-380, 1944.
PASCHOALINO, J.E.; FERREIRA, V.L.P.; POMPEU, R.M. Aptidão das variedades de batatinha Bintje e Radosa para processamento de fritas à francesa e congeladas e purê congelado. Coletânea do Instituto de
Tecnologia de Alimentos, v.6, p.431-444, 1975.
PASCHOALINO, J.E.; FERREIRA, V.L.P.; TOCCHINI, R.P.; BERNHARDT, L.W. Avaliação de cultivares de batatinha (Solanum tuberosum L.) para processamento na forma de fritas congeladas.
Coletânea do Instituto de Tecnologia de Alimentos, v.13, p.33-57,
1983.
PEREIRA, A.S. Composição química, valor nutricional e industrialização. In: REIFSCHNEIDER, F.J.B. (Coord.) Produção de batata. Brasília: Linha Gráfica, 1987. p.12-28.
PRESSEY, R. Potato sucrose synthetase: purification, properties, and changes in activity associated with maturation. Plant Physiology, v.44, p.759-764, 1966.
SALAMONI, A.I.; PEREIRA, A. da S.; VIÉGAS, J.; CAMPOS, A.D.; CHALÁ, C.S. de A. Variância genética de açúcares redutores e matéria seca e suas correlações com características agronômicas em batata.
Pesquisa Agropecuária Brasileira, v.35, p.1441-1445, 2000.
SCHIPPERS, P.A. The relationship between specific gravity and percentagem dry matter in potato tubers. American Potato Journal,
v.53, p.111-122, 1976.
SOMOGY, M. Determination of blood sugar. Journal of Biological
Chemistry, v.160, p.69-73, 1945.
